• Environmental quality. In particular by accommodating a large fraction of generation from renewable-energy sources.

Technologies

Technologies used to modernize the T&D systems must be implemented systematically and nationwide, particularly with respect to the transmission system, to achieve maximum benefit. R&D will be important for reducing costs and improving performance, but except in a few cases, breakthroughs are not needed. In fact, most of the technologies already exist and could be deployed now.

Included among these key modernizing technologies are the following:

  • Advanced equipment and components. Power electronics and high-voltage AC and DC lines offer the potential for long-distance transmission and grid operation that are more efficient. Power electronics both for transmission (Flexible Alternating Current Transmission System—FACTS) and distribution (Custom Power) currently exist and have been deployed in limited applications. Corresponding higher-voltage long-distance lines and substations could be deployed by 2020. High-voltage DC systems can be more economical than AC under some conditions, especially when lines must be underground or underwater, and several DC lines are already in operation. Cost-effective electric storage would be valuable in smoothing power disruptions, preventing cascading blackouts, and accommodating intermittent renewable-energy sources. Some storage technologies (e.g., compressed air energy storage and perhaps advanced batteries) will be ready for deployment before 2020, but significant development is still needed.

  • Measurements, communications, and control. Modern T&D systems will have the ability to gather, process, and convey data on the state of the system far more effectively than can be done at present. Sampling voltage, frequency, and other important factors many times per second will give operators a much clearer picture of changes in the system and enhance their ability to control it. Most of the necessary technologies are available and have been installed to a limited degree. The communications and control software needed to take full advantage of these technologies could use further development but should be ready by



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